Proxy Mobile Internet Protocol version 6 (PMIPv6) is a network layer scheme for offering mobility management on the Internet, and the protocol enables a Mobile Node (MN) to carry out link switching without interrupting the communication in progress.
The mobility management mechanism of PMIPv6 is that a network equipment acts as an agent to perform mobility management for the MN, so that the MN remains accessible through its IPv6 Home Network Prefix (HNP) and/or its IPv4 Home address when the MN moves on any link in a PMIPv6 Domain, viz. the IPv6 Home Network Prefix and/or the IPv4 Home address of the MN remain unchanged, the MN believes that no movement occurs to itself in the IP layer, and the ongoing service of the MN can remain to be continued.
FIG. 1 is a frame diagram of the PMIPv6 Domain. As shown in FIG. 1, the PMIPv6 Domain is mainly composed of a Local Mobility Anchor (LMA), a Mobile Access Gateway (MAG) and the MN, wherein the network is composed of the LMA and the MAG.
FIG. 2 is a frame diagram of an Evolved Packet System (EPS). In order to maintain the competence of the Third Generation Mobile Communication System in mobile communication filed, the network performance thereof must be improved, and the network construction and operation costs must be reduced. Thus, the standardization working group of the 3rd Generation Partnership Project (3GPP) is now working on the study of the evolution of the next generation of the core network system—Evolved Packet Core (EPC), for the purpose of providing higher transmission rate and shorter transmission delay for the users. The EPC system supports the access of Evolved Universal Terrestrial Radio Access Network (E-UTRAN); the EPC system also supports the access of Non-3GPP Access Network, e.g. Worldwide Interoperability for Microwave Access (WiMAX) Access Network.
As shown in FIG. 2, in the case when a User Equipment (UE) is in a non-roaming state, UE1 accesses the EPC through a Non-3GPP Access Network (including trusted and untrusted Non-3GPP Access Network), while UE2 accesses the EPC through the E-UTRAN. The UE herein refers to the MN described in the PMIPv6 protocol. The network elements shown in FIG. 2 also include: a Mobility Management Entity (MME), a Serving Gateway (S-GW), a Packet Data Network Gateway (PDN GW or P-GW), a Home Subscriber Server (HSS), a 3GPP Authentication and Authorization Accounting server (3GPP AAA Server), and an Evolved Packet Data Gateway (ePDG).
Wherein the MME is responsible for control-plane related work such as mobility management, the processing of non-access stratum signaling, and user context management; the S-GW is an access gateway equipment connected with the E-UTRAN, and is used for transmitting data between the E-UTRAN and the PDN GW; the P-GW is a boundary gateway between the 3GPP EPS and Internet Protocol (IP) services provided by the Home Public Land Mobile Network (HPLMN), and is responsible for the access of the IP services and the transmission of data between the EPS and an IP service network.
The EPS supports the use of PMIPv6 protocol between the S-GW and the P-GW and between the WiMAX access network and the P-GW, wherein the P-GW has the function of an LMA, the S-GW and the WiMAX access network have the function of MAG. The UE herein refers to the MN described in PMIPv6 protocol.
Non-3GPP wireless access network shown in FIG. 2 comprises the following two types:
Trusted Non 3GPP Access: a trust relation exists between the 3GPP Network and the non 3GPP access network, the non 3GPP access network can directly access the P-GW through an S2a interface, wherein the PMIPv6 can be used at the S2a interface.
Untrusted Non 3GPP Access: a trust relation does not exist between the 3GPP Network and the non 3GPP access network, the non 3GPP access network has to access the ePDG of the 3GPP network firstly, and then access the P-GW through an S2b interface. Herein a secure tunnel is established between the UE and the ePDG so as to ensure the secure transmission of the data between the UE and the 3GPP network. Wherein the PMIPv6 is used at the S2b interface.
The LMA is a home proxy of the MN within the PMIPv6 domain. Furthermore, the LMA is a topological anchor of the Home Network Prefix of the MN, is used for managing the binding state of the MN, wherein each binding state is corresponding to a Binding Cache Entry (BCE) managed by the LMA, and the content of the BCE comprises: an MN Identifier, an IPv6 Home Network Prefix and/or IPv4 Home Address currently used by the MN, service information currently used (viz. Access Point Name, APN).
The LMA can intercept data packets whose destination address is the IPv6 Home Network Prefix or the IPv4 Home Address of the MN within the management domain of the LMA, and can forward the data packets to a Proxy Care-of Address (Proxy-CoA) registered by the MN in the BCE. The Proxy-CoA is the address of the MAG, wherein the MAG is an access router which is used for tracking the movement of the MN, the movement of the MN herein comprises that the MN access or leave the access link; the MAG is also used as proxy for the MN attached to the access link of the MAG and for managing the signaling related to the mobility of the MN, including transmitting a Proxy Binding Update (PBU) to the LMA of the MN and receiving a Proxy Binding Acknowledgement (PBA) from the LMA. Through the PBU and the PBA, the MAG acts as an agent for the MN to establish, in the LMA, the binding state between the IPv6 Home Network Prefix or the IPv4 Home Address of the MN and the Proxy CoA, and the LMA stores the binding state as a BCE. After receiving a data packet whose destination address is the IPv6 Home Network Prefix or the IPv4 Home Address of the MN from the LMA, the MAG forwards the data packet to the MN.
The IPv6 Home Network Prefix is a permanent IPv6 address prefix which is allocated by the network to the MN for use in the PMIPv6 domain. The IPv4 Home Address is a permanent IPv4 address which is allocated by the network to the MN for use in the PMIPv6 domain. A standard IP routing mechanism will send an IP data packet which is sent to the IPv6 Home Network Prefix or the IPv4 Home Address of the MN to the PMIPv6 domain thereof, and the LMA is responsible for intercepting the IP data packet, then searching the BCE stored therein, and forwarding it to the corresponding MAG according to the Proxy CoA stored in the BCE, and then the MAG forwards the IP data packet to the corresponding MN according to the destination address or address prefix of the data packet.
Binding is an association relation between the IPv6 Home Network Prefix and/or the IPv4 Home Address of the MN and the Proxy CoA.
As shown in FIG. 1, in the PMIPv6 Domain, when the MN is switched from accessing the MAG1 through Interface 1 to accessing the MAG2 through Interface 2, the network needs to judge whether it is necessary to provide address preservation for the MN according to whether the MN has the ability of preserving address between different interfaces. The address preservation indicates that the IP address (including the IPv6 Home Network Prefix and/or the IPv4 Home Address) used at the interface before the switching of the MN is allocated to the interface for use after the switching of the MN. When the IPv6 Home Network Prefix and/or the IPv4 Home Address of the MN remain unchanged, the IP service used by the MN before the switching can be continually used after the switching, and the continuity of the service can be realized. If the network does not provide address preservation, the MN will obtain at Interface 2 an IPv6 Home Network Prefix and/or IPv4 Home Address different from that at Interface 1, and after the switching, the IP service previously performed at Interface 1 cannot be continued at Interface 2, and the IP service will be interrupted, viz. the switching fails.
Currently, if the network side knows that the MN has the ability, the network will preserve the address for the MN; if the network side does not know whether the MN has the ability, or if the network knows that the MN does not have the ability, the network will not provide the address preservation.
At present, as the network does not preserve the address before the switching for the MN under the cases that the network side cannot acquire whether the MN has the ability of address preservation between different interfaces, as a result, even for the MN which has the ability of address preservation between different interfaces, the network cannot preserve the address.